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Author: search.filters.author.Jirakittidul, KittimonHas files: No

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    Effects of Annealing Temperature and Time on Properties of Thermoplastic Polyurethane Based on Different Soft Segments/Multi-Walled Carbon Nanotube Nanocomposites
    (2023-01-01)
    Jirakittidul, Kittimon
    ;
    Limthin, Darawan
    ;
    Mahithithummathorn, Sarita
    ;
    Phaewchimphlee, Seenam
    Typically, polymer chains can move under the annealing process, resulting in an ordered structure arrangement. This causes an improvement in nanocomposite properties and in the dispersion of filler. In this research, annealed thermoplastic polyurethane (PU)/multi-walled carbon nanotube (MWCNT) nanocomposites were studied to investigate the effect of annealing on the selective dispersion of MWCNTs. PU matrices were composed of two different soft segments, i.e., polyether (PU-Ether) and polyester (PU-Ester). Nanocomposites were prepared by the melt mixing process and annealed at 80 to 120 °C for 6 to 24 h. The increases in annealing time and temperature resulted in microphase separation in segmented PU and the orientation of crystalline structures in the segregated hard domain. Nanocomposites showed higher electrical conductivity after annealing. This implies that the movement of PU chains during heat treatment encouraged the development of the MWCNT network. However, the increase in ordered structures could obstruct the MWCNT network, resulting in lower electrical conductivity levels. Considering the selective dispersion of MWCNT in PU matrices, it was found that MWCNTs dispersed in soft segments of PU-Ether, leading to a significant decrease in elongation at the break after annealing. On the other hand, a decrease in elasticity of PU-Ester nanocomposites was not observed as a result of MWCNT dispersal in hard segments.
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    Acid modified multiwalled carbon nanotubes condition by reflux
    (2019-09-25)
    Jirakittidul, Kittimon
    ;
    Vittayakorn, Naratip
    ;
    Manrean, Rawijee
    ;
    Pornteeranawapat, Natchanun
    ;
    Neamyooyong, Saichon
    Nanomaterials, especially carbon nanotubes (CNTs), show excellent combinations of thermal, mechanical and electrical properties. However, as-produced CNTs are entangled and form agglomerates, due to their several micron lengths. Therefore, the dispersion efficiency of CNTs is limited. We decreased the length and improved dispersion with acid modified multiwall-CNTs (A-MWCNTs) formed by a reflux method. MWCNTs were modified with an acid mixture of sulfuric acid and nitric acid at the ratio of 3:1 by volume. The reflux temperature and time were varied between 80 to 120 °C and 10 to 30 min. FTIR found an increase in carboxylic acid groups on the surfaces with increasing reflux temperature and time. Therefore, A-MWCNTs showed good dispersion in polar solvents; i.e. water, DMF and DMAc. Furthermore, A-MWNCT lengths were shortened with increased reflux temperature and time. Carboxylic acid groups on A-MWCNT surfaces decreased the electrical conductivity by two orders of magnitude. However, epoxy resin in which the A-MWCNTs, modified at 120 °C and 30 min were encapsulated, showed better conductivity, since the shortest MWCNT lengths and the carboxylic groups on the A-MWCNT surfaces allowed good dispersion in epoxy resin.
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    Selective dispersion of multi-walled carbon nanotubes in segmented polyurethane with different melt mixing process
    (2017-01-01)
    Jirakittidul, Kittimon
    ;
    Khrongsakun, Krittaya
    ;
    Khongkhaw, Kannika
    ;
    Nernplod, Kusuman
    Polyurethanes (PU) have been widely used in many applications since their properties can be tailored as desire. In order to improve their electrical property, PU is incorporated with multi-walled carbon nanotubes (MWCNT). The effects of different mixing times and temperatures on selective dispersion of MWCNT in segmented PU were studied. Furthermore, segmented PU based on two different soft segments; i.e. polyester (PU-ester) and polyether (PU-ether), were used. PU/MWCNT nanocomposites were prepared by an internal mixer for 4-12 minutes at 190-210°C. FESEM, DSC and LCR meter were used to characterize morphology and thermal properties. It was found that MWCNT were dispersed in soft segment of PU-ether. Good MWCNT dispersion was able to achieve at high temperature with short mixing time or low temperature with long mixing time. On the other hand, PU-ester/MWCNT nanocomposites, MWCNT preferred to disperse in hard segment and could be dispersed well in PU-ester at low mixing temperature.